The Value of Rebiopsy in GIST

When a cancer progresses, rebiopsy for genomic testing may reveal valuable new information. In "Andrea"’s case, a subtle new variation in her tumor’s genotype was now detected and suggested a change in therapy might be beneficial.

About "Andrea"

In this molecular profile, our fictional patient, Andrea, is a 45 year-old Caucasian woman who had experienced progressive abdominal fullness for several months, followed by weight loss and bloody stools. She was diagnosed with gastrointestinal stromal tumor (GIST) that had spread to her liver.

She was treated with imatinib and initially responded very well. But after two years, her tumors started to grow. A repeat biopsy of one of her tumor masses was analyzed by further molecular testing and revealed an important KIT mutation that may explain why she became resistant to the therapy.

Actionable Information

• 40-50% of GIST patients on imatinib will develop progression within 2 years.
• While initial biopsies of GIST commonly show mutations in exons 9 or 11 prior to therapy, biopsies of tumors at the time of progression may show new mutations in the binding pocket of the receptor (exons 13 and 14) or in the activation loop (exon 17).
• Sunitinib has been approved for the treatment of patients with GIST who progress while on therapy with imatinib.
• In a recent study, median progression-free survival with second-line therapy with sunitinib was 7.8 months in patients with secondary KIT mutations in exons 13/14, compared to only 2.3 months in patients with secondary KIT mutations in exons 17/18 (p=.016)¹

References

1. Heinrich MC, Maki RG, Corless CL, et al. Primary and secondary kinase genotypes correlate with the biological and clinical activity of sunitinib in imatinib-resistant gastrointestinal stromal tumor. J Clin Oncol. 2008;26:5352-9.

Note: This fictional, composite story, which includes data from actual representative patient cases, conveys how information from comprehensive genomic testing may impact treatment for management and care of people suffering from cancer.